Water-resistant coating and method of producing the same



Patented Mar. 3, 1931 PATENT OFFICE LESTER KIRSCHBRAUN,

OF LEONIA, NEW JERSEY, ASSIGNOR TO THE FLINTKOTE COM- PANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS WATER-RESISTANT COATING AND METHOD OF PRODUCING THE SAM Ho Drawing.

This invention relates to water resistant coatings and method of producing the same.

More particularly the invention has reference to protective coatings for surfaces which are employed under conditions which render them liable to attack by water, moisture, corrosion or other deteriorating action.

One of the objects of the invention is to provide a coating for the purpose described, in which shall be highly resistant to permeation by water or other agency, tending to cause decay or similar injury to the surface over which it is applied.

Another object is to provide a coating of the above described character in which the water resistant material is itself protected against abrasion (Jr deformation tending to injure same and expose the surface protected thereby to destructive influences, such as the corrosive action of water, acids and the like. Another object is to provide a method by which the protecting layer for the water resistant material may be easily applied so as to combine and form with said material an eflicient and lasting protectivecoating for the surface covered therewith.

A further important object of the invention is to provide in conjunction with the water resistant coating, a protective surfacing therefor which will not only save the water repellant material from injury by the abrasive action of materials in contact therewith, but will also functionto increase the water resistance of the water repellant film. The invention finds particular utility in protecting metal surfaces, and especially metal pipes, which may, in certain instances, as for example those, used as lines for transporting gas, oil, etc. be buried underground and thus be subject to corrosionand to the pressure and abrasive action of the overlying soil. It should be understood, however, that the foregoing is merely given as an example of one use to which the invention may be applied, and that other uses may suggest, themselves for the protective coatings herein to be described and claimed.

It has been known that surfaces such asherein contemplated maybe made substantially waterproof by coating the same with Application filed September 23, 192?. Serial No. 221,617.

fluid substances which are capable of setting or hardening to a film adapted to serve as a moisture impervious membrane, preventing access of moisture to the surface. Thus, bituminous materials, such as asphalt or the like, have been employed in molten condition,

for this purpose. The use of such materials in heated liquid condition, however, entails some considerable difficult-y, which has, to a certain extent, been overcome by employing these substances in the form of cut-backs, that is, compounds formed by dissolving in a volatile solvent, which latter may readily evaporate and leave the water-proofing substance as a continuous film over the surface to which the cut-back has been applied. Volatile solvents which answer this purpose are, however, costly and by virtue of their generally inflammable nature, present considerable danger in use. Furthermore, in order to build up a coating of sufiicient thickness for this purpose it is necessary to apply several coats of the cut-back, so that a great deal of time is lost between successive applications.

In accordance wlth the present invention,

the waterproofing media is provided in a form in which it may be applied at normal temperatures in relatively heavy layers of desired thickness, as by brushing, spraying or dipping the surface to be coated, and from which form it is capable of drying and setting to a substantially waterproof film. Preferably, tl1erefore,-the waterproofing substance comprises a dispersion of bituminous material such as asphalt or the like in an aqueous vehicle containing a mineral powder, soap, casein, or other type of material, which has functioned as a dispersing agent in the production of the dispersion. In this type of dispersion, upon evaporation of the aqueous vehicle which constitutes the exter nal phase of the dispersion, the dispersed upon the character of the dispersion, the na-" ture of the dispersingagent, and other factors. In studying the resistance of these films, I have found that their permeability is difi'erent toward solutions of different electrolytes. Thus, with bitumen-clay type dispersions, solutions of acids, and certain salts of the alkaline earth metals, especially the oxides and hydroxides, are substantially unable to permeate the dried films of these dis persions, whereas on the other hand, solutions of alkali metal salts seem to penetrate such films with greater ease. The difference of behavior of the dispersion films towards different electrolytes may be attributed to the peculiar structure of the films themselves. As these films are formed by the evaporation of the water constituting the external phase of the dispersion, the substance used as the dispersing agent becomes concentrated into segregated film areas in the interfaces between the asphalt particles, which latter thereupon coalesce through these more or less persistent film areas.

The aforedescribed property of the dried films in exhibiting varying degrees of resistance to various electrolyte solutions is utilized in the present invention by employing, in conjunction with the water-free film, arigid protective surfacing which will not only afford the necessary protection to the film against mechanical injury, but may also contain substances belonging to that class of materials which when in solution are incapable of permeating the film. Thus, by using as a protective layer over the waterproof film, a cementitious material containing lime or lime salts, the aforesaid property may be advantageously utilized. For this purpose Portland cement may be applied as will hereinafter be explained, as a separate layer over the previously dried coating of bituminous dispersion.

In a somewhat similar manner magnesium salts may be incorporated either in the Port land cement itself or by employing the well known magnesium oxy-chloride type of cement as the outer covering. It has been proposed to provide a coating of this type having a surfacing layer of rigid material by dusting dry cement over a substantially wet film of bituminous dispersion, so that the water contained in the dispersion would hydrate the cement and cause the setting of the latter. With this procedure, however, the hydration and setting of the cement to a hard coherent body is dependent upon ab-' straction of water by capillary action from the wet dispersion film over which the cement is applied, and during the setting action there is a continual evaporation of water from the exposed surface of the cement layer. Where these conditions prevail, and the cement is not completely hydrated, the outer surface is not uniform and is composed of substantial quantities of powdery or readily as disintegrable material. and hence does not provlde the requisite protective properties to the bituminous film underneath. This difficulty is particularly met with in those instances where the coating is applied in hot and arid regions, over metallic pipes to be laid underground for conveying gas, oil, etc. and these conditions are generally such that unless special precautions are taken to maintain an excess of water in contact with the cement, the water is completely evaporated from the coating before it has had opportunity to hydrate the cement to produce a coherentand non-powdery layer. In accordance with the present invention, the foregoing difficulty is eliminated, and the necessity for taking the aforesaid special precautions is obviated, by applying the cement in the form r of a water slurry to the bituminous dispersion coating, after the latter has completely set and dried. p

In carrying out the invention, the surface to be treated may he first completely covered with the bituminous dispersion which may be manufactured in accordance with the process described in United States Patent No. 1,615,303, datedJ'anuary 25th,1927. This dispersion may comprise material such as asphalt of 100 to 200 F. melting point as the dispersed phase, with water as the continuous phase. The dispersing agent may comprise any one or a mixture of inert substances. such as clays, bentonites, metallic oxides. silicates, and the like. The dispersion should be such as to enable it to be brushed or sprayed onto the pipe or other surface, and if the dispersion is too viscous for such application. it may 100 be readily thinned, as by dilution with water to the desired extent. Where it is preferable to apply the coating by dipping a sectionof pipe into the dispersion, the consistency, if it is too thick, may likewise be reduced to the 5 extent necessary to permit the desired amount of material to cling tothe surface of the pipe and adhere thereto upon withdrawal of the pipe section from the bath of the dispersion.

After the dispersion coating has been ap- 110 plied and built up to the desired thickness. the wateris allowed to evaporate so as to form a substantially dry film over the surfacetreated. In accordance with one embodiment of the invention there may be then applied over 115 the dried bituminous coating, an external layer of cementitious material containing minor quantities of bitumen. the purpose of the latter being to impart increased toughness to the cementitious layer and to render it less 120 liable to fracture or similar injury which may expose the underlying film. This external layer is preferably composed of a relatively heavy slurry of hydraulic cementitious material with which the bitumen, prefe-rahly in 125 aqueous dispersed form, is combined in uniform admixture therewith. The bitumen which is thus combined with the cementitious material is preferably of such character as will permit it to flow and fuse together at 130 ordinary temperatures, the melting point of the bitumen used for this purpose being preferably below 185 F.

The combination of the bitumen with the cement slurry may be most readily effected by employing the bitumen in the form of an aqueous dispersion. For this purpose, the

dispersion may be made with dispersing agents such as those heretofore enumerated, and in accordance with the methods of the aforesaid issued patent. The dispersion may be used in any suitable quantities for this purpose, the essential requirements in this regard being that the Portland cement'in the wet composition, predominate over the bitumen content thereof, and that sufficient water be present to completely wet all the cement. Thus, one part by volume of bitumen dispersion containing about 50-60% of asphalt may be combined with two to six parts by volume of Portland cement, it being understood that higher relative quantities of cement produce the harder and more rigid protective surfacing. Water in suitable quantities to produce a slurry of desired consistency may obviously be added to this mixture. In one experiment in which this type of operation has been carried out, and in which a very satisfactoryv protective surfacing was produced by this means,

, so that the asphalt constituted the aforesaid composition contained approximately three parts by volume or about 200 parts by weight of Portland cement and one part by volume, or 55 parts by weight of a dispersion containing about 55% of asphalt, about 14% by weight of the Portland cement in the mixture on a dry basis. 7

This slurry, brought to the desired consistency with water, may be brushed or sprayed onto the dry bituminous film so as to provide, when the cement has completely set and hardcried, a rigid and toughened external protecting layer of suitable thickness.

It will be appreciated that the outermost cementitious layer as thus provided may be slightly porous and permit water to penetrate therethrough. Such water, however, as does penetrate the outer surfacing, will carry with it small amounts of the lime constituents of the cement, and such constituents, coming into contact with and substantially wetting the film underneath, will function in the manner above described to form effective barriers against permeation of liquid through the film.

Where it is not essential that the external surfacing layer be toughened by the presence of bituminous material therein, it may be desirable to employ a slurry composed wholly of hydraulic cement, as the outer layer for protecting the dried dispersion formed on the surface treated. This slurry may be applied in the manner already described, and when dry will function in the manner above set forth, although it will obviously be more fragile than, and will lack the characteristic toughness of, an external cementitious layer containing bitumen.

In another mode of carrying out the pres ent invention, a small amount of hydraulic cement may be combined with the bituminous coating applied over the surface being treated in order to increase the toughness of said coating. For this purpose I may mix with the bituminous dispersion, hydraulic cement preferably in the form of a slurry, prior to application of the dispersion over the surface to be treated. The amount of cement so employed may comprise, say 20 to 25% by weight of the dispersion. Such quantity of cement as is selected for admixture with the bituminous dispersion may be combined therewith either by adding the dry cement to the dispersion, or by previously making a slurry of the dry cement and then combining the slurry with the aqueous dispersion. The combined mixture of dispersion and hydraulic cement is then brushed or sprayed orotherwise applied over the pipe or other surface, whereupon the composition is permitted to completely set and dry to a tough waterproof film, which may then be provided with an outer protective layer of hydraulic cement as above described.

In certain instances, it may be desirable to introduce into the external surfacing an excess of lime or similar substances, in qrder to insure the presence of such substantes in whatever water or other liquid may penetrate the surfacing and tend to wet the bituminous coating underneath. lVhere lime is used for this purpose, it maybe combined with the slurry in amounts ranging up to 15%, more or less, by weight of the solid constituents of the slurry. Another material which may be used for this purpose and one which possesses certain additional advantages is calcium chloride, since this salt functions to quickly harden and accelerate the setting of the cement. In practicing this feature of the invention, it should be obvious that substances other than calcium chloride may be mixed with the cement slurry in order to promote and accelerate the setting action. Where calcium chloride is used, the above described results may be achieved with quantities of this salt ranging up to 2%, more or less, by weight of the cement in the slurry.

I claim as my invention:

1. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying to said surface a coating comprising an aqueous bitumen-pitch type dispersion, allowing said coating to dry and form a film, increasing the water resistance of said dry film by superposing over said film an aqueous slurry of hydraulic cementitious material and permitting the slurry to dry and form a coating to protect the film from abrasion.

2. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying to said surface a coating comprising an aqueous bitumen-pitch type dispersion, allowing said coating to dry and form a film, increasing the water resistance of said dry film by superposing over said film a slurry of hydraulic cement and a relatively small quantity of an agent capable of accelerating the setting of the cement and permitting the slurry to dry and form a coating to protect the film from abrasion.

3. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying over said surface a coating comprising an aqueous bitumen-pitch type dispersion. allowing said coating to dry and form a film, and increasing the water resistance of said dry film by superposing over said film a slurry composed of hydraulic cement and bitumen.

4. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying over said surface a coating comprising an aqueous bitumen-pitch type dispersion. allowing said coating to dry I and form a film, and increasing the water resistance of said dry film by superposing over said film a slurry composed of hydraulic cement. bitumen, and an agent adapted to accelerate the setting of the cement.

5. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying over said surface a coating comprising an aqueous bitumen-pitch type dispersion, allowing said coating to dry and form a film, and increasing the Water resistance of said dry film by superposing over said film a slurry composed of a major proportion of hydraulic cement and a. minor proportion of bitumen.

6. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying over said surface a coating comprising an aqueous bitumen-pitch type dispersion, allowing said coating to dry and form a film, and increasing the water resistance of said dry film by superposing over said film a slurry composed of a major proportion of hydraulic cement and a minor proportion of bitumen in aqueous dispersed form.

7. In the method of treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying over said surface a coating comprising an aqueous bitumen-pitch type dispersion, allowing said coating to dry and form a film, and increasing the water resistance of said dry film by forming over said film a rigid adherent layer composed of hydraulic cementitious material and bitumen.

8. A corrodible surface having a protective coating adhering thereto comprising a bituminous film, and an outer layer united with said film and covering the same, said outer layer being composed of a major proportion of hydraulic cementitious material and a minor proportion of bitumen.

9. A corrodible surface having a protective coating adherent thereto comprising a film composed of the water-free residue of an aqueous bitumen-pitch type dispersion, and a. layer overlying said film and united therewith consisting of hydraulic cementitious material and a minor proportion of bitumen.

10. A corrodible surface having an adherent.protective coating comprising a film of bituminous material, and a coherent layer of hydraulic cementitious material containing minor proportions of bitumen adhering to and overlying said film to protect same against mechanical injury, said layer also containing an excess of lime adapted to increase the Water resistance of said film.

11. In the method of-treating surfaces whereby to inhibit corrosion thereof, the steps which comprise applying to said surface a coating comprising an aqueous bitumen pitch type dispersion, allowing said coating to become substantially dry so as to form a film, increasing the, Water resistance of said dry film by superposing over said film an aqueous slurry comprising Portland cement.

In testimony whereof I affix my signature.

LESTER KIRSGHBRAUN. 

